Process

ABSTRACT

A novel process for the preparation of a 16-imino-17-aza-steroid of the formula ##STR1## wherein A is selected from the group consisting of hydrogen and tritium comprising reacting a compound of the formula ##STR2## wherein A has the above definition and R is an acyl of an organic carboxylic acid of 1 to 8 carbon atoms with an oximation agent to obtain a compound of the formula ##STR3## reacting the latter with an agent to form an acid chloride to obtain a compound of the formula ##STR4## reacting the latter with ammonia to obtain a compound of the formula ##STR5## reacting the latter with an alkali metal hypohalite in the presence of a base to obtain a compound of the formula ##STR6## wherein X is a halogen and reacting the latter with a base to obtain the desired compound and the novel compound of formula I wherein A is tritium and the novel intermediates of formulae III, IV, V and VI.

STATE OF THE ART

The compound of formula I wherein A is hydrogen is described byBoaventura et al [1978 in Abstracts: VII Congresso Latinoamericano deFarmacologia Sao Paulo and P. Hunt and S. Clements-Jewery: A steroidderivative, R 5135, Antagonizes the GABA/Benzodiazepine receptorinteraction. Neuropharmacology Vol. 20, p. 357-361, 1981] and itspharmacological properties are described therein.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a novel process for thepreparation of the compounds of formula I and the novel intermediatesformed therein.

It is another object of the invention to provide the novel compound offormula I wherein A is tritium.

These and other objects and advantages of the invention will becomeobvious from the following detailed description.

THE INVENTION

The novel process of the invention for the preparation of a16-imino-17-aza-steroid of the formula ##STR7## wherein A is selectedfrom the group consisting of hydrogen and tritium comprises reacting acompound of the formula ##STR8## wherein A has the above definition andR is an acyl of an organic carboxylic acid of 1 to 8 carbon atoms withan oximation agent to obtain a compound of the formula ##STR9## reactingthe latter with an agent to form an acid chloride to obtain a compoundof the formula ##STR10## reacting the latter with ammonia to obtain acompound of the formula ##STR11## reacting the latter with an alkalimetal hypohalite in the presence of a base to obtain a compound of theformula ##STR12## wherein A has the above definition and X is a halogenand reacting the latter with a base to obtain the desired compound offormula I.

Examples of suitable carboxylic acids for the acyl of R are alkanoicacids such as formic acid, acetic acid, propionic acid, butyric acid,isobutyric acid, valeric acid and hexanoic acid but acetic acid ispreferred.

The oximation agent is preferably an alkyl nitrite such as tert.-butylnitrite and the reaction is preferably effected in the presence of astrong base such as potassium tert.-butylate. The acid chloride formingagent is preferably thionyl chloride but other chlorinating agents maybe used and the reaction is effected at low temperatures preferably.

The hypohalite with a formula of MOX wherein X is a halogen and M is analkali metal is preferably sodium hypochlorite and the reaction iseffected in the presence of a base such as sodium hydroxide. However,the reaction may also be effected with bromine in the presence of analkali metal alcoholate such as sodium methylate. The transformation ofa compound of formula VI into the compound of formula I is effected inthe presence of a base such as sodium hydroxide and is preferablyeffected at reflux in an organic solvent such as methanol.

In a preferred mode of the process of the invention, A is hydrogen and Ris preferably acetyl. The preferred oximation agent is nitrous acid,alkali metal nitrite such as sodium nitrite or a lower alkyl nitritesuch as tert.-butyl nitrite or isopentyl nitrite. When a salt of nitrousacid is used, the reaction is preferably effected in the presence of anacid such as a mineral acid like hydrochloric acid or an organic acidsuch as acetic acid. When an ester of nitrous acid is used, the reactionis preferably effected in the presence of a strong base such as analkali metal alkylate like potassium tert.-butylate. The oximationreaction is preferably effected at room temperature or with cooling. Theformation of the acid chloride is effected under standard conditions,preferably using thionyl chloride or phosphorus pentachloride.

In a more preferred mode of the process, the oximation is effected withtert.-butyl nitrite in the presence of a strong base and the acidchloride is formed with thionyl chloride and the compound of formula Vis reacted with sodium hypochlorite in the presence of sodium hydroxide.

The compounds of formulae III, IV, V and VI are novel intermediatecompounds and preferred are those wherein A is hydrogen. The novelcompound of formula I wherein A is tritium is novel and is useful as aradioactive marker for the GABA receptor.

The compounds of formula II wherein A is hydrogen and R is acetyl isdescribed in French Pat. No. 942,260 and German Pat. No. 2,062,911 andthe compounds wherein R is other than acetyl may be made therefrom byknown methods.

The compounds of formula II wherein A is tritium may be prepared byreacting a compound of the formula ##STR13## described in U.S. Pat. Nos.2,902,498 and 2,902,410 and in German patent DT 2.062.911 with areactant for protecting the 17-keto group to form a compound of theformula ##STR14## wherein Z is a keto protective group, reacting thelatter with tritium to obtain a compound of the formula ##STR15##wherein T is tritium atom, optionally submitting to a separation forrecovering the sought 5β-isomer of formula C and reacting the latterwith a reducing agent to obtain a compound of the formula ##STR16##subjecting the latter to an acylation agent to obtain a compound of theformula ##STR17## wherein R has the above definition, optionallysubmitting to a separation for recovering the sought 3α-isomer andreacting the same with an oxidation agent to obtain a compound of theformula ##STR18## and reacting the latter with a reagent able to releasethe 17-keto protective group to form the compound of the formula##STR19##

In a preferred mode of the invention, the reagent for forming the17-keto protective group is ethylene glycol in the presence of p-toluenesulfonic acid and the isomers of formulae C and E are separated bychromatography. The reduction of the compound of formula C is effectedwith an alkali metal hydride such as sodium borohydride or potassiumborohydride and the acylation is effected with acetic anhydride toobtain R as acetyl. The oxidation of the compound of formula E iseffected with a mild oxidation agent such as pyridinium chlorochromateand the hydrolysis of the 17-keto protective group is effected with anacid such as hydrochloric acid when >C═Z is a dioxolane group.

At the time of the reaction of the products of formula VI to products offormula I, the product of formula ##STR20## may be obtainedintermediately but normally this product is not isolated. Certain stagesof the process described above may also be carried out without isolationof the intermediate product. In addition, it is possible to passdirectly from products of formula III to products of formula V withoutisolating the product of formula IV.

The products of formula I may be present in two tautomeric forms. Inaddition to the form described above, there also exists a form offormula I_(Z) and there is in fact an equilibrium as follows: ##STR21##Lastly, the products of formula I contain an amine function and may bepresent in the form of salts with acids, in particular mineral acids andit has been possible to prepare 16-imino-17-aza-5β-androstane3α-ol-11-one hydrochloride. Examples of other acids are sulfuric acid,nitric acid, hydrobromic acid, phosphoric acid, etc.

In the following examples there are described several preferred examplesto illustrate the invention. However, it should be understood that theinvention is not intended to be limited to the specific embodiments.

EXAMPLE 1 16-imino-17-aza-5β-androstane-3α-ol-11-one STEP A:3α-acetoxy-16-oximino-5β-androstane-11,17-dione

At ambient temperature, 500 ml of tert.-butyl nitrite were added all atonce to a solution of 500 g of 3α-acetoxy-5β-androstane-11,17-dione in2.5 liters of anhydrous methylene chloride and the solution was adjustedto 0° C. Then, over a period of 30 minutes at 0° and 2° C., a solutionof 201 g of potassium tert.-butylate in 1.5 liters of tert.-butanol wasadded thereto and after stirring for 2 minutes at 0° C., the solutionobtained was introduced into 1.835 liters of a solution of Nhydrochloric acid in methanol at 0° C. over a period of 45 minutes. Thesolution was washed 3 times with 2.5 liters of distilled water, driedand evaporated to dryness under reduced pressure at 40° C. The resinobtained was added to 500 ml of ethyl acetate and the mixture wasrefluxed until dissolved and the solution was cooled and the solvent wasevaporated under reduced pressure to obtain 613 g of crystallineproduct. The latter was triturated 3 times in ether and dried at 40° C.to obtain 405.6 g of 3α-acetoxy-16-oximino-5β-androstane-11,17-dione inthe form of white crystals melting at 267° C.

STEP B:3α-acetoxy-17-chloro-16,17-seco-5β-androstanonitrile-16-11,17-dione

Over 15 minutes, 5 g of the product of Step A were introduced in smallamounts into 50 ml of thionyl chloride cooled to 0° C. and the mixturewas stirred for 1 hour at about 0° C. and then was evaporated to drynessunder reduced pressure at about 40° C. The residue was taken up inmethylene chloride and the solution was poured into a mixture of ice andwater. The decanted organic phase was washed first with water, then with5% sodium bicarbonate and finally with water. The wash waters wereextracted twice with methylene chloride and the combined organic phaseswere dried, and evaporated to dryness. The residue was crystallized fromisopropyl ether by cooling and filtering. The product was washed withisopropyl ether and dried at 90° C. to obtain 4.58 g of3α-acetoxy-17-chloro-16,17-seco-5β-androstanonitrile-16-11,17-dionemelting at 212° C.

STEP C:3α-acetoxy-17-amino-16,17-seco-5β-androstanonitrile-16-11,17-dione

At 20° C. and with stirring, 7 ml of 22° Be ammonium hydroxide wereadded dropwise to a solution of 700 mg of the product of Step B in 21 mlof acetone and after standing for 90 minutes at 20° C., the mixture waspoured into water. The mixture was extracted with methylene chloride andthe organic phase was washed with water, dried and evaporated to drynessunder reduced pressure. The residue was crystallized by concentration inan acetone-isopropyl ether mixture to obtain 615 mg of3α-acetoxy-17-amino-16,17-seco-5β-androstanonitrile-16-11,17-dionemelting at 190° C. and having a specific rotation of [α]_(D) ²⁰ =+57°±2°(c=0.6% in chloroform).

STEP D:3α-chloro-17-aza-17-carboxy-16,17-seco-5β-androstanonitrile-16-11-one

Under nitrogen, a suspension of 45 g of the product of Step C in 1.125liters of ethanol was cooled to 10° C. and then over a period of 5minutes, 337.5 ml of N sodium hydroxide were added. After cooling to 0°C., 112 ml of 47°/50° chlorometric "eau de javelle" extract were addeddropwise over 15 minutes and the mixture was stirred for 90 minutes at0° C. The reaction medium was poured into 3.365 liters of iced water andthe neutral fractions were extracted three times with 650 ml ofmethylene chloride. The combined organic phases were re-extracted with300 ml of water and the combined aqueous phases at 10° and 15° C. wereacidified with N hydrochloric acid. The mixture was extracted withmethylene chloride and the organic phase was washed with water andevaporated to dryness under reduced pressure at 35° C. The 36.8 g ofwhite crystals were taken up in 40 ml of acetone and 400 ml of isopropylether were added. Crystallization was initiated and after standing for awhile at 4° C., the mixture was filtered. The product was washed twicewith isopropyl ether and dried under reduced pressure to obtain 31.6 gof 3α-chloro-17-aza-17-carboxy-16,17-seco-5β-androstanonitrile-16-11-onemelting at 212° C. (decomposition).

STEP E: 16-imino-17-aza-5β-androstane-3α-ol-11-one

68 ml of 10N sodium hydroxide were introduced under nitrogen into asuspension of 31.5 g of3α-chloro-17-aza-17-carboxy-16,17-seco-5β-androstanonitrile-16-11-one in600 ml of methanol and after refluxing for one hour, the mixture wascooled to 20° C. The mixture was evaporated to dryness under reducedpressure and the residue was taken up in 350 ml of water. After standingat +4° C., the mixture was filtered and the product was washed with icedwater and dried at 40° C. to obtain 15.6 g of16-imino-17-aza-5β-androstane-3α-ol-11-one melting at 260° C.

EXAMPLE 2 16-imino-17-aza-5β-androstane-3α-ol-11-one hydrochloride

At room temperature, 20 g of 16-imino-17-aza-5β-androstane-3α-ol-11-onein 400 ml of anhydrous methanol was stirred until dissolution occuredand while stirring, 27 ml of 2.5N hydrochloric acid in methanol wereadded dropwise under nitrogen. Then 100 ml of isopropyl ether were addedand the mixture was filtered. The product was washed with an isopropylether-methanol mixture (1--1) and dried to obtain 14.6 g of16-imino-17-aza-5β-androstane-3α-ol-11-one hydrochloride. Then, a secondlot of 2.7 g were obtained which after crystallization from the motherliquors had a Rf=0.47 (chloroform-methanol 50--50; acetic acid 5%).

Analysis: Calculated: %Cl 10.5 Found: 10.39

Various modifications of the process of the invention may be madewithout departing from the spirit or scope thereof and it is to beunderstood that the invention is to be limited only as defined in theappended claims.

What we claim is:
 1. A process for the preparation of a16-imino-17-aza-steroid of the formula ##STR22## wherein A is selectedfrom the group consisting of hydrogen and tritium comprises reacting acompound of the formula ##STR23## wherein A has the above definition andR is an acyl of an alkanoic acid of 1 to 8 carbon atoms with an alkylnitrite to obtain a compound of the formula ##STR24## reacting thelatter with a chlorinating agent to form an acid chloride to obtain acompound of the formula ##STR25## reacting the latter with ammonia toobtain a compound of the formula ##STR26## reacting the latter with analkali metal hypohalite in the presence of a base to obtain a compoundof the formula ##STR27## wherein A has the above definition and X is ahalogen and reacting the latter with a base to obtain the desiredcompound of formula I.
 2. The process of claim 1 wherein A is hydrogenand R is acetyl.
 3. The process of claim 1 wherein the oximation agentis tert.-butyl nitrite and the reaction is effected in the presence of astrong base.
 4. The process of claim 1 wherein the chlorinating agent isthionyl chloride.
 5. The process of claim 1 wherein the alkali metalhypohalite is sodium hypochlorite.
 6. A compound of the formula##STR28## wherein A is tritium.